Howto implement a generic Filter for IQuerable for all Entities ? #2528

6 Answer(s)

• 

  0

  enisn created 3 years ago

  Support Team .NET Developer

  In your scenario, you can use add a where clause to specify the type, so you can access the Id property. The following extension method should work:

  public static class QueryExtensions
  {
      public static IQueryable<T> IncludeFilterIds<T>(this IQueryable<T> queryable, List<Guid> ids)
          where T : Entity<Guid>
      {
          return queryable.WhereIf(!ids.IsNullOrEmpty(), t => ids.Contains(t.Id));
      }
  }
  

  Then you can call normally:

    query = query.IncludeFilterIds(filterIds);
  

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  3
• 

  0

  hakan.uskaner created 3 years ago

  Hi Ensin,

  i thank you for your quick response. This works lika charm. Do you also got an idea for the second part on howto limit the properties with an paramter List<string> propertyList to generate a dynamic select statement which then can be added to the query like describes above.

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• 

  0

  enisn created 3 years ago

  Support Team .NET Developer

  I think you need something like that: https://stackoverflow.com/a/16517768/7200126

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• 

  0

  hakan.uskaner created 3 years ago

  I thank you. I will take a look at it

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• 

  0

  hakan.uskaner created 3 years ago

  For thos who also searched around for this infos:

  My solution for filtering properties and id now looks like this.:

     public static class QueryableExtensions
      {
          public static Expression<Func<T, T>> DynamicSelectGenerator<T>(string filterProperties)
          {
              string[] entityProperties;
              if (filterProperties.IsNullOrEmpty())
  
                  // get Properties of the T
                  entityProperties = typeof(T).GetProperties().Select(propertyInfo => propertyInfo.Name).ToArray();
              else
              {
                  // at least Id must be include besides a property (Case sensitive !)
                  if (!filterProperties.Contains("Id"))
                      filterProperties +=",Id";
                      
                  entityProperties = filterProperties.Split(',');
              }
  
              // input parameter "o"
              var xParameter = Expression.Parameter(typeof(T), "o");
  
              // new statement like "new Data()"
              var xNew = Expression.New(typeof(T));
  
              // create initializers
              var bindings = entityProperties.Select(o => o.Trim())
                  .Select(o =>
                  {
  
                  // property "Field1"
                  var mi = typeof(T).GetProperty(o);
  
                  // original value "o.Field1"
                  var xOriginal = Expression.Property(xParameter, mi);
  
                  // set value "Field1 = o.Field1"
                  return Expression.Bind(mi, xOriginal);
                  }
              );
  
              // initialization "new Data { Field1 = o.Field1, Field2 = o.Field2 }"
              var xInit = Expression.MemberInit(xNew, bindings);
  
              // expression "o => new Data { Field1 = o.Field1, Field2 = o.Field2 }"
              var lambda = Expression.Lambda<Func<T, T>>(xInit, xParameter);
  
              // return expression
              return lambda;
          }
  
  
          // Extend IQuerable to use DynanimcSelector for Select
          public static IQueryable<T> Select<T>(this IQueryable<T> source, string parameters)
          {
              return source.Select(DynamicSelectGenerator<T>(parameters));
          }
  
          // Extend IQuerable to be able to use IncludeFilter
          public static IQueryable<T> IncludeFilter<T>(this IQueryable<T> queryable, List<Guid> filterIds, string filterProperties)
                  where T : Entity<Guid>
          {
              return queryable
                  .WhereIf(!filterIds.IsNullOrEmpty(), t => filterIds.Contains(t.Id))
                  .Select(filterProperties);
          }
  
      }
  

  Within an Repository i then call it like this, and also set Sorting (because DefaultSorting can fail if you omit the default parameter used for sorting) :

  var query = ApplyFilter((await GetQueryableAsync()), filterText, name, description);
   // Add IncludeFilter to Query and adjust sorting
  query = query.IncludeFilter(filterIds, filterProperties);
  if (!filterProperties.IsNullOrEmpty())
    sorting = filterProperties.Split(",").First();
  
  query = query.OrderBy(string.IsNullOrWhiteSpace(sorting) ? MyEntityConsts.GetDefaultSorting(false) : sorting);
  return await query.PageBy(skipCount, maxResultCount).ToListAsync(cancellationToken);
  

  To be able to use these both fields for my InputDto i used this:

   public class GlobalInputDto : PagedAndSortedResultRequestDto
      {
          /// Filter for specific Ids.
          public List<Guid> FilterIds { get; set; }
  
          /// Filter Properties (case-sensitive) p.E. "Name,Description,Id"
          public string FilterProperties { get; set; }
  
      }
  

  To use it in for an Entity you only need to replacein your InputDtos PagedAndSortedResultRequestDto inheritance through GlobalInputDto

  Hope this helps..

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  1
• 

  0

  enisn created 2 years ago

  Support Team .NET Developer

  Thank you for your well-implemented sharing @hakan.uskaner.

  I'm closing this issue now

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